The present invention concerns a linear guide to support a sliding element, as, for example, a door or part of a machine.
The linear guides comprise a fixed longitudinal support and a mobile part on rollers that slides along the longitudinal support holding a sliding unit suspended or bearing from above.
In known guides the fixed longitudinal support is generally shaped so as to present one or two plane sliding races upon which at least two rollers for each race roll charging radially Generally the roller cursor runs astride the guide and the cross-sectional encumbrance is given by the sum of the dimensions of the guide plus the dimensions of the rollers; this solution is shown in FIG. 1. Opposite versions are also known in which the guide has the inner sliding races and in these versions the guide is large enough to contain also the roller cursor and the cross-sectional encumbrance is similar to the version previously described.
The main purpose of the present invention is to offer a linear guide that features a smaller transversal section compared to known guides, at equal roller dimensions and load capacity.
This linear guide belongs to the type of guides with the sliding cursor within the fixed longitudinal support and is characterised by a cursor that comprises a main cursor bearing a main group of rollers and at least one auxiliary cursor which bears an auxiliary group of rollers, the auxiliary cursor being adjustable in respect of the main cursor in order to move with respect to the other group. The two cursors carry rollers that can roll along four races defined within a longitudinal cavity that has a parallelogram cross-section and is formed within the fixed longitudinal support in order that one of its diagonals coincides with the line of action of the load supported by the guide and to have a longitudinal aperture along one of the vertexes crossed by said line in order to allow the passage of the parts that connect the cursor to the sliding element, so that the latter and the cursor may slide along said support. One group of rollers can roll along the two races that will take the load and the other group can roll along the other two races, but the adjustment means allow to transfer the engagement of each group of rollers from the two races to the opposite two, so that the guide can work with the sliding element above or below the guide, the load being borne by the four rollers of the main group in any case. This characteristic of being able to use the guide with the sliding element above or else below the guide is conventionally called xe2x80x9cguide inversionxe2x80x9d. The longitudinal cavity will preferably have a square section and the description herein will relate to such square section embodiment.
The auxiliary cursor, preferably set at the centre of the main cursor, is fixed to the latter by means of a coupling in sliding-guiding engagement, sliding and fastening screws and spacing screws, all together suited to adjust the relative movement of the two cursors, as it will be explained in detail with the example of embodiment.
In one embodiment of the present invention, in which the load transmitted by the sliding element is applied above the guide, the main group of rollers bears at least one pair of rollers that are longitudinally spaced from one another and charge on a first common lower race and bears at least a second pair of longitudinally spaced rollers charging on a second common lower race positioned at 90xc2x0 with respect to the first race; the auxiliary cursor is positioned between the said first and second pairs of rollers, preferably at the centre of the main cursor, and bears at least two rollers at 90xc2x0 from one another that respectively charge upon the two upper races.
According to said embodiment we have a guide bearing at least six rollers, four of which charge upon the lower races supporting the load transmitted by the sliding element and two are just slightly engaged on the two lower races so that the cursor is held in all transversal directions during its sliding along the guide.
The advantages of this guide lie in that, given the same load capacity, compared to a known guide, it allows for a greater compactness and lightness, a protected positioning of the roller system and the fact that all the rollers conveniently charge on the respective races in order to provide a sliding free of undesirable transversal jolting and the possibility of guide inversion.